Sealing system for underwater installation



s. s. HELMUS 3,485,056

Dec. 23, 1969 Dec. 23, 1969 s. s. HELMUS SEALING SYSTEM FOR UNDERWATER INSTALLATION 2 Sheets-Sheet 2 Filed Sept. 19, 1968 33 Bill United States Patent 3,485,056 SEALING SYSTEM FOR UNDERWATER INSTALLATION Sydney S. Helmus, San Jose, Calif., assignor to Lockheed Aircraft Corporation, Burbank, Calif. Filed Sept. 19, 1968, Ser. No. 760,807 Int. Cl. B63c 11/00 US. Cl. 61-69 7 Claims ABSTRACT OF THE DISCLOSURE Sealing system for establishing a fluidtight seal between a submersible capsule and an underwater installation; the seal being established by reducing the water pressure inside said capsule with respect to the ambient water pressure. The preferred seal assembly comprises a metalto-metal seal backed up by a resilient O-ring type seal.

Background of the invention This invention relates to a method and apparatus for making a fluidtight connection between an underwater installation and a submersible capsule. The underwater installation might be of any type used in mining or other deep sea exploration and production activities. However, for purposes of this description, the underwater installation will be referred to as a wellhead celler of the type considered for use in the petroleum industry. The submersible capsule may likewise take a variety of forms but for purposes of the present description the capsule is of the type having means for providing an atmospheric environment so that personnel may perform operations at the wellhead cellar after the capsule has been moved into fiuidtight engagement therewith.

The invention is especially adapted to deep water installations situated at depths beyond which a diver can safely and readily work, for example, depths below approximately 300 feet. In any event, the sealing system of the present invention should preferably be capable of operation in water depths extending to approximately 1,000 feet or greater.

In addition the sealing system to which the invention is directed should be capable of functioning even though the mating surfaces between the capsule and underwater installation are gouged or somewhat fouled with rust scale and marine growth, etc.

The sealing system is an extremely important facet of the subject deep water operations because failure of the seal could result in loss of life to the personnel performing the underwater operations.

An advantage of the present invention is the provision of a seal system which utilizes ambient water pressure to both establish and maintain a fluidtight seal between the submersible capsule and the underwater installation.

A further advantage of the invention is the provision of a double sealing arrangement comprised of a metal-tometal face type seal which is backed up by a resilient seal element which forms an O-ring type seal at the radially outer edge of the metal-to-metal seal.

Other and further objects and advantages of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred em bodiments of the present invention and the principles thereof and what are now considered to be the best modes contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

3,485,056 Patented Dec. 23, 1969 Brief description of the drawings FIG. 1 is a diagrammatic view illustrating an exemplary method by which a submersible capsule may be lowered down toward an underwater installation;

FIG. 2 is a longitudinal view, partially in section, illustrating certain details of the submersible capsule and the underwater installation;

FIG. 3 is a sectional view illustrating details of the seal assembly just prior to initial engagement of the submersible capsule with the underwater installation; and,

FIG. 4 is a sectional view illustrating details of the seal assembly after the submersible capsule and the underwater installation have been engaged in fluidtight relation.

Description of the preferred embodiment Referring to FIG. 1 of the drawing there is illustrated an exemplary application of the invention in use in a body of water 21. In order to facilitate the application of the invention, an opera-ting station taking the form of a floating barge 23 is shown floating on the surface of the water 21 in a position approximately above a preselected underwater installation such as a wellhead cellar 25.

As shown in FIG. 1 a submersible capsule 27 is being moved downwardly toward the wellhead cellar 25. The capsule 27 is divided into an upper compartment 29 and a lower compartment 31. The compartment 29 provides an atmospheric environment for one or more human personnel who will perform various operations at the wellhead cellar 25.

A conduit package 33 is connected between the surface station 23 and the submersible capsule 27. The conduit package 33 contains air lines, conduits for electrical conductors and conduits for hydraulic connetions. As also shown in FIG. 1 a cable 35 extends between the wellhead cellar 25 and the submersible capsule 27.

Referring now to FIG. 2 in conjunction with FIG. 1 it will be observed that the lower compartment 31 of the capsule 27 is provided with a winch or cable reeling mechanism 37. Thus the capsule is caused to descend downwardly into engagement with the wellhead cellar 25 by winding up the cable 35 on the winch mechanism 37.

As the capsule 27 is being lowered or pulled down towards the wellhead cellar 25 the lower compartment '31 is exposed to sea water since the lowermost portion of the capsule is provided with a cylindrical opening. However, a hatch 39 which separates the upper compartment 29 from the lower compartment 31 is securely closed so that the atmospheric environment of the upper compartment is preserved.

The lowermost end of the capsule 27 is provided with a flared skirt 41 which facilitates in guiding the capsule down onto an upwardly projecting annular probe 43 formed on the top of the wellhead cellar 25.

As best shown in FIG. 3 an annular protuberance or shoulder 45 is formed on the very top of the probe 43. An

-angled wall member 47 extends downwardly from the shoulder 45 until it meets a cylindrical outer wall 49 formed on the outer surface of the probe 43. Just above the flared skirt or mouth 41 of the capsule 27 there is formed an annular inner wall 51. When the capsule is received on the probe 43 of the wellhead cellar 25 there will exist a small annular gap between the outer wall 49 of the probe and the inner wall 51 of the capsule 27. This gap or space is denoted at X.

It should be further noted that the inner annular wall 51 of the capsule 27 extends upwardly to a point where it intersects an internal shoulder 53. At the conjunction of the annular wall 51 and the shoulder '53 a resilient annular seal element '55 is securely positioned such as by ce- 3 ment or mechanical fasteners such as the shouldered shear ledge 57 shown in FIG. 4.

In FIG. 3 the capsule 27 is shown just after the flared mouth 41 thereof has been guidingly received on the probe 43 of the wellhead cellar 25. In FIG. 3 the capsule 27 has been aligned upon the probe 43 but the lower compartment 31 of the capsule is still in communication with the ambient sea water which flows through the annular space X between the surfaces 49 and 51. As the capsule 27 continues to move downwardly a lower corner portion 59 of the seal will contact the angled surface 47 formed on the cellar probe 43. Just as soon as contact is made between the corner 59 of the seal and the angular surface 47 a fluidtight seal will be formed preventing sea water from flowing into or out of the lower compartment 31 of the capsule 27.

Referring back to FIG. 2, the capsule 27 is provided with a main conduit 61 which is preferably provided with a flexible lower end which terminates in the vicinity of the bottom portion of the flared mouth 41. The conduit 61 is provided with a first branch conduit 62 which communicates through a valve 64 which when open will allow sea water to flow into or out of the conduit 62. A second branch conduit 64 leads from the main conduit 61 into the atmospheric upper compartment 29 of the capsule 27. The conduit 65 is also provided with a valve 67. The valve 67 communicates fluid from the conduit 65 to a sump or drain 69 which may in turn be connected through a conduit not shown to the sea water outside the capsule 27 for purposes of overboard discharge. A third branch conduit 71 leads from the conduit 61 to a motor driven pump 73. A check valve 75 is situated in the conduit 71 between the pump and that end of conduit 71 which communicates with the sea water outside of the capsule 27.

As the capsule descends toward the probe 43 formed on the wellhead cellar 25, the valve 64 is opened so that sea water may continually circulate through main conduit 61 and branch conduit 62. The valve '64 might be termed an equalizing valve since it provides for equal water pressure inside the lower compartment 31 of the capsule 27 and the ambient sea water located Outside the capsule 27.

When the lower portion 59 of the seal 55 contacts the angled wall 47 of the cellar probe 43 circulation of sea water through the conduits '61 and 62 ceases as the seal 55 makes contact with angled wall 47 along the entire surface thereof. Since the seal '55 is now in contact with the angled wall 47 of the probe 43 sea water can no longer flow from the space denoted X into the lower compartment 31 of the capsule 27.

After the resilient seal 55 has made contact with the angled wall '47 of the wellhead cellar and formed a fluidtight seal therebetween operation of the cable reeling mechanism 37 is discontinued and the valve 64 is closed. At this point in the operation it should be observed that the water pressure inside the lower compartment 31 is equal to the water pressure outside the capsule 27 and that this water pressure is extremely great at the depth in which the subject apparatus is situated. However, the upper compartment 29 of the capsule in which the operators reside is maintained at atmospheric pressure and therefore there is a large pressure differential between the compartments 29 and 31.

At this stage of the operation an operator in the compartment 29 opens the valve 67 which communicates the sump or drain 69 at atmospheric pressure in the compartment 29 with the sea water located in the lower compartment 31 (via conduits '65 and 61). Due to the great pressure differential between the atmospheric pressure in compartment 29 and the much higher water pressure in the compartment 31 water will be rapidly displaced via conduits 61 and 65 from the compartment 31 to the sump or drain 69. This water displacement from compartment 31 into compartment 29 will continue until the pressure in compartment 31 equals the pressure in compartment 29 which is the pressure of one atmosphere or atmospheric pressure.

In actual practice the pressure dilferential between compartments 31 and 29 is so great that once the valve 67 is opened water in compartment 31 is immediately displaced to the drain 69 in compartment 29. When this happens both the compartment 29 and the compartment 31 are placed at atmospheric pressure which pressure is much smaller than the extremely high pressure of the sea water surrounding the outer surfaces of the capsule 27. Due to this great pressure differential the entire capsule 27 will move rapidly downwardly onto the probe 43 of the wellhead cellar 25.

This sequence of the operation may be better understood by comparing FIG. 3 with FIG. 4. In FIG. 3 the resilient seal member 55 is shown just before contact with the angled wall 47 of the cellar probe 43. Even after the seal 55 has contacted the angled wall 47 the metal surfaces 53 of the capsule and 45 of the cellar probe will not be in sealing contact. It is only after the valve 67 is opened and the capsule 27 moves rapidly downwardly onto the probe 43 that a possible fluidtight metal-to-metal seal is formed by engagement of the surface 45 with the surface 53. However, it should be noted that an adequate seal will be formed between seal 55 and the surface of angled wall 47 of probe 43. In addition to a possible metal-to-metal seal, the surfaces 45 and '53 cooperate to form a supporting arrangement for preventing the seal 55 from being crushed owing to the extreme weight of the capsule '27.

The completed seal between the capsule 27 and the probe 43 on the wellhead cellar 25 is clearly shown in FIG. 4. In FIG. 4 a metal-to-metal contact has been formed between the cellar probe surface 45 and the internal shoulder surface 53 of the capsule 27. In addition, the resilient seal 55 has been compressed into fluidtight engagement throughout the entire length of the angled wall 47 of the cellar probe 43. Thus the possible metalto-metal seal between the surfaces 45 and 53 is backed up by the resilient seal member 55 thereby forming a double seal arrangement whenever the metal-to-metal seal exists.

It should be further observed that the extremely high ambient sea water pressure is at all times present in the annular area denoted at X and tends to compress the resilient seal 55 upwardly into fluidtight engagement with the outer edge of the metal-to-metal contact formed between the surfaces 45 and 53. Thus an extremely eflicient sealing arrangement is effected between the capsule 27 and the well-head cellar 25. Moreover, portions of this sealing arrangement are a relatively simple construction which are easily accessible for observation, replacement or repair and at the same time provides for both a fluidtight metal-to-metal seal backed up by a fluidtight resilient seal member. In addition to these advantages the sealing arrangement of the present invention also utilizes the high pressure of the ambient sea water to effectuate an even tighter seal since the sea water acts agfainst the resilient member to compress it into tight engagement with the outer edge of the metalto-metal contact arrangement or seal.

A still further advantage of the metal-to-metal contact arrangement or seal formed by the surface 45 of the cellar probe 43 and the surface 53 of the capsule 27 resides in the fact that a solid metal support base is established between the capsule 27 and the wellhead cellar 25. Thus the supporting surface between the wellhead cellar and the capsule also forms a possible metalto-metal seal between the capsule and the wellhead cellar.

It may also be observed from FIG. 4 that the area 81 of the resilient seal member 55 forms an O-ring type seal which backs up the outer edge or face of the metalto-metal contact arrangement or seal formed between the surfaces 53 and 45. Further, the resilient seal of the present invention combines the properties of both a simple gasket and an O-ring type gasket. As a pressure differential is created between the interior and exterior of the capsule 27 the sea pressure acting on the capsule and throughout the annular area denoted at X compresses the elastomeric seal 55 as a simple gasket. When metal-to-metal contact is made between the surfaces 45 and 53 the elastomeric seal 55 is captive having a residual pressure caused by the squeezing action and now functions as an interference seal. This means any increase in the pressure differential automatically increases the pressure in the elastomeric seal 55. Therefore the rubber seal pressure is a summation of sea pressure (or differential) and the induced residual pressure in the seal itself. It is the residual pressure that provides intimate contact between the rubber and the joint surfaces, thereby closing the possible leakage path.

In the preferred embodiment of the invention the angle or slope of the wall 47 is aproximately 45 with respect to horizontal. This sloping surface of the wall 47 allows falling or settling debris and marine life to slide away from the sealing surface and in addition acts as a force multiplier or wedge which helps prevent sea water blow-in. The resilient seal 55 is preferably constructed of styrene-butadiene rubber because of its Waterresistant and rubber-like properties. The cross-section and durometer of the resilient member are such as to preferably cause a compression of approximately in the seal to allow conformance with surface irregularities such as gouges, marine life protuberances or other surface roughness.

After the capsule 27 has moved down into sealed fluidtight relation with the wellhead cellar 25 as shown in FIG. 4, the motor driven pump 73 (see FIG. 2) is actuated. The pump 73 pumps any remaining water out of the lower compartment 31 and an inner cavity 83 of the wellhead cellar 25 so that a hatch 85 which seals off an inner portion of the cellar 'will be exposed. After the sea water has been pumped out of the lower compartment 31 and the area 83 of the wellhead cellar an operator in the upper compartment 29 opens the hatch 39 and descends into the lower compartment 31.

The operator then actuates a pair of rams 87 WhiCh are located on diametrically opposite walls of the capsule 27. These rams actuate pivoted latching dogs 89 to move the dogs into a latched or locked position underneath an annular flange 91 formed on the cellar probe 43. The latching dogs 89 serve as a mechanical tie-down and are employed to resist any forces which might tend to override the sealing forces and allow leakage or lift-off.

The operator then descends into the wellhead cellar 25 and opens the hatch 85 which seals off the interior of the wellhead cellar. At this point men and equipment may be freely passed between the capsule and the interior or the wellhead cellar so that a variety of operations may be performed at the wellhead cellar. Exemplary operations which might be performed at the wellhead cellar include replacement of blow-out preventers, repairing Christmas tree components, clean-up operations and various other workover operations which are typically required at a wellhead installation.

After the operations have been completed inside the wellhead cellar the operator closes the hatch 85 thereby sealing off the interior of the cellar. The cable may now be released from the wellhead cellar 25 and reeled in on the winch 37. The ram mechanisms 87 are then retracted so that the dogs 89 are unlatched from the annular flange 91. After the dogs have been released from the flange 91 the operator ascends into the upper compartment 29 and closes the hatch 39 thereby sealing off the upper compartment 29 from the lower compartment 31.

The valve 64 is now opened and since the ambient sea water is at a much greater pressure than the lower compartment 31 of the capsule, the lower compartment is quickly filled with sea water by way of the branch conduit 62 and the main conduit 61. After the sea water has reentered the lower compartment 31 a neutral condition exists between the capsule 27 and the wellhead cellar 25. Thus the capsule 27 is no longer being forced downwardly upon the cellar probe 43 since the water pressure inside the capsule 27 is equal to the water pressure outside the capsule. The operator inside the upper compartment 29 now signals the surface station 23 and personnel at the surface station begin pulling the capsule 27 upwardly to the water surface Where it is retrieved.

While the present invention has been shown and described with respect to a submersible capsule moving into sealed engagement with a fixed underwater installation it should be recognized that the principles of the invention could be employed to interconnect two movable objects in deep water, such as a seal connection between two submersible capsules.

While I have illustrated and described preferred embodiments of my invention, it is to be understood that these are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

What is claimed is:

1. A seal for establishing fluidtight engagement between a submersible capsule and an underwater installation, said seal comprising, a flat annular surface and an angled wall surface on an end portion of said underwater installation that faces the submersible capsule, said capsule having a fiat annular surface for face-to-face mating engagement with the flat annular surface of said underwater installation, said capsule further having surfaces providing a recessed cavity with respect to the angeled wall of the underwater installation, and a resilient deformable sealing element disposed in said recessed cavity, said resilient sealing element having an angled surface facing the angled wall of the underwater installation, whereby upon engagement of said capsule with said underwater installation the resilient sealing member initially engages the angled wall to form an annular, relatively small width, fluidtight seal and whereby continued axial movement of the capsule onto the installation establishes a larger and tighter sealed area between said resilient member and the angled wall until said flat annular surfaces engaged in annular, metal-to-metal contact.

2. A seal assembly as set forth in claim 1 wherein a radially outer annular area of said resilient member is exposed to the ambient water.

3. A seal as set forth in claim 1 wherein said recessed cavity and said angled wall are shaped so as to conform said resilient deformable element into a resilient back-up seal for the metal-to-metal contact.

4. A seal assembly as set forth in claim 3 wherein said resilient back-up seal is formed into an O-ring type seal.

5. A seal assembly as set forth in claim 4 wherein auxiliary latch means are provided for mechanically fastening said capsule to said installation to insure that said seal assembly is maintained fiuidtight.

6. A seal assembly as set forth in claim 1 wherein said metal-to-metal contact forms a fiuidtight seal.

7. A seal assembly as set forth in claim 6 wherein said deformable element is a back-up seal for the fluidtight seal formed by said metal-to-metal contact.

References Cited UNITED STATES PATENTS 1,803,526 5/1931 Finn 61-69 1,834,798 12/1931 Nair et al. 6l69 3,265,130 8/1966 Watkins 6169 3,353,364 11/1967 Blanding et al. 61-69 J. KARL BELL, Primary Examiner 

